Computing systems require memory in order to function. This computer memory is referenced by address and the full range of memory available to the system is known as the address space. When a problem with a computer system is being investigated the contents of this address space is of vital importance as it shows the state of the processes within the system.
In order to access the contents of the address space for diagnostic purposes a system dump can be generated or carried out. However, a system dump is a time-consuming process that causes a significant delay to other processes within the system.
In a busy production environment this dump delay can cause numerous secondary problems, such as tasks timing-out and themselves abnormally ending (ABENDing) causing further system dumps to be generated or carried out, and work backing-up to the point where the system becomes overloaded. The knock-on effect of these dump delays can be very serious, often more serious than the problem for which the dump was originally carried out. In extreme cases, the system may not recover back to a normal running state without a complete system reset.
The dump delays may also cause the system to appear unresponsive to the end-user, and the build-up of unprocessed work may prevent new work from being accepted.
Due to the problems described, it is common practice for customers to disable certain system dumps from being carried out at all, so that critical diagnostic information is lost. All these problems lead to reduced customer satisfaction and increased service costs.
In addition to system dumps, other diagnostic tools are limited by the current machine architecture because of the performance overhead of employing them. One example is system tracing, where trace records are written out at pre-defined points in the processing, containing partial dumps of storage for particular areas of interest. The performance overhead of taking such trace records often means it is not viable to run with full tracing enabled in a production system, such that once again, vital diagnostics are lost if a failure occurs and problem determination is required.